Hectograph transfer sheets and master sheets and webs are well-known in the art. Conventional hectograph transfer sheets and webs carry a layer of pressure-transferable duplicating composition, and conventional master sheets and webs are designed to receive mirror-reverse images of hectograph composition from the transfer sheet under the effects of writing or typing pressure applied against the rear surface of the master sheet. The imaged master sheet or web is mounted on a hectograph duplicating machine, generally a spirit duplicating machine, and a plurality of correct-reading duplicate copies are produced. Generally, the hectograph composition contains undissolved hectograph dye and the copy sheets are moistened with a liquid spirit solvent such as an alcohol. However, in some cases the hectograph composition is microporous and contains pressure-exudable fluid ink, and the copies are made by pressing the imaged master against dry copy sheets.
It is desirable to be able to duplicate an imaged master sheet or web from time to time as additional copies are required, such as of printed forms, instruction sheets, clothing patterns, and the like. This is not possible with conventional hectograph master sheets and webs, without substantial loss of copy quality, because the images on the hectograph master migrate into and/or over the master paper surface during periods of storage so that subsequent reduplication efforts produce weak copies and/or blurred copies, i.e., copies of unsatisfactory color intensity and sharpness.
It has been proposed by U. S. Pat. No. 4,018,162 to apply an oil-barrier coating to both surfaces of a continuous master web in order to prevent the master paper from absorbing the oily ink from porous duplicating images applied to the master web, either directly or when the imaged web is rolled up. Such coatings are designed to prevent the master images from drying out during storage. However, they are solvent-applied coatings which are not pressure-adhesive, and which contain porous filler to make them receptive and which are not inert to the conventional spirit solvents. Thus, they have an affinity for the spirit solvents, absorb such solvents to cause the master sheet to swell and curl, and cause soluble dye to be dissolved out of the master images to form broadened or filled-in master images which produce duplicate images which are less sharp or have a blurred appearance.
It is also desirable to be able to image hectograph master webs and sheets in modern automatic line-pressure scribing machines such as plotters, scanners or drafting machines. Such machines have a mechanical stylus pen which is automatically guided over a copy sheet to form images or pictures corresponding to those on a remote original sheet or instructions from a computer program. It has not been found possible to use liquid hectograph ink in such stylus pens to produce masters which can be duplicated. Also, attempts to image conventional hectograph master units using the pressure applied by such stylus pens have been unsuccessful, because the pressure is too low to produce any satisfactory transfer of hectograph composition from the transfer layer to the master sheet, even in cases where the hectograph transfer layer carries an adhesive supercoating.
Attempts to improve the pressure-sensitivity of hectograph master webs and sheets by applying conventional pressure-adhesive soft coatings to the receptive surface thereof have resulted in the creation of other problems, particularly in the case of imaged masters which are duplicated by means of pressure, as in U.S. Pat. No. 4,018,162. Convention soft pressure-adhesive coatings, such as those consisting of paraffin wax and mixtures thereof with lesser amounts polyisobutylene resin, are so soft and adhesive that they stick to and transfer to the master web or sheet, or to parts of the pressure-duplicating machine, so as to be useless for such purpose.